The present invention relates to the head structure of golf clubs and, more particularly, to an improvement in the head structure of iron clubs.
In general, iron clubs are intended primarily for second, third and bunker shots rather than tee shots, and they are used often for hitting shots from the bare ground, a sandy place and so on as well as from turf. Accordingly, conventional iron clubs are designed so that the club head is made in one body from a metallic material such as soft iron, stainless steel or the like in order to prevent the club head, and in particular its sole, from being readily damaged by a pebble or sand when hitting a ball.
The metal material, however, does not permit variety in the design of such clubs because of its large specific gravity. For example, it is desirable particularly for beginners and powerless golfers that the center of gravity of the head is located at a relatively lower part thereof. This is achieved by increasing the thickness of the lower part of the club head including the sole, but the thickness of middle and upper portions of the head should be reduced in order to maintain the weight of the head as a standard level, such reduced thickness resulting in the defect of decreased distance of a struck ball. Thus, it has been believed with conventional iron clubs that good operability and high performance are not compatible with each other. Further, the face surface of the conventional head is made of a hard metal, and hence its repulsive force is small. Accordingly, the use of hard metal is not always preferable from the viewpoints of the direction and distance of the ball.
Recently, there has been proposed a golf club head comprising a metal core and a fiber reinforced resin layer enclosing the core as, for example, disclosed in Japanese laid-open document No. 59-82060. This type of golf club head has the merits of permitting variety of design thereof because the volume of metal material is rather small, and of achieving a greater distance because of its large repulsive force at the striking face, as compared with the conventional type. The metal core behind the striking face, however, unfavorably affects the feel when hitting the ball, and tends to cause the ball to take off from the face immediately after a short period of impact, this being undesirable for direction of the ball. Further, since the core and the enclosing layer are formed of entirely different materials, it is difficult to connect them together by an adhesive and there is the possibility that the enclosing layer may peel off from the core. In addition, an upwardly extended metal core prevents the center of gravity from being positioned at a considerably lower part of the head to the satisfaction of non-expert golfers.